The present invention relates to vaccine formulations comprising papilloma virus proteins, either as fusion proteins, truncated proteins, or truncated fusion proteins. The invention further embraces methods for producing capsomeres of the formulations, as well as prophylactic and therapeutic methods for their use.
Infections with certain high-risk strains of genital papilloma viruses in humans (HPV)xe2x80x94for example, HPV 16, 18, or 45xe2x80x94are believed to be the main risk factor for the formation of malignant tumors of the anogenital tract. Of the possible malignancies, cervical carcinoma is by far the most frequent: according to an estimate by the World Health Organization (WHO), almost 500,000 new cases of the disease occur annually. Because of the frequency with which this pathology occurs, the connection between HPV infection and cervical carcinoma has been extensively examined, leading to numerous generalizations.
For example, precursor lesions of cervical intraepithelial neoplasia (CIN) are known to be caused by papilloma virus infections [Crum, New Eng. J. Med. 310:880-883 (1984)]. DNA from the genomes of certain HPV types, including for example, strains 16, 18, 33, 35, and 45, have been detected in more than 95% of tumor biopsies from patients with this disorder, as well as in primary cell lines cultured from the tumors. Approximately 50 to 70% of the biopsied CIN tumor cells have been found to include DNA derived only from HPV 16.
The protein products of the HPV 16 and HPV 18 early genes E6 and E7 have been detected in cervical carcinoma cell lines as well as in human keratinocytes transformed in vitro [Wettstein, et al., in PAPILLOMA VIRUSES AND HUMAN CANCER, Pfister (Ed.), CRC Press: Boca Raton, Fla. 1990 pp 155-179] and a significant percentage of patients with cervical carcinoma have anti-E6 or anti-E7 antibodies. The E6 and E7 proteins have been shown to participate in induction of cellular DNA synthesis in human cells, transformation of human keratinocytes and other cell types, and tumor formation in transgenic mice [Arbelt, et al., J. Virol., 68:4358-4364 (1994); Auewarakul, et al., Mol. Cell. Biol. 14:8250-8258 (1994); Barbosa. et al., J. Virol. 65:292-298 (1991); Kaur, et al, J. Gen. Virol. 70:1261-1266 (1989); Schlegel, et al., EMBO J., 7:3181-3187 (1988)]. The constitutive expression of the E6/E7 proteins appears to be necessary to maintain the transformed condition of HPV-positive tumors.
Despite the capacity of some HPV strains to induce neoplastic phenotypes in vivo and in vitro, still other HPV types cause benign genital warts such as condylomata acuminata and are only rarely associated with malignant tumors [Ikenberg, In Gross, et al., (eds.) GENITAL PAPILLOMAVIRUS INFECTIONS, Springer Verlag: Berlin, pp., 87-112]. Low risk strains of this type include, for example, HPV 6 and 11.
Most often, genital papilloma viruses are transmitted between humans during intercourse which in many instances leads to persistent infection in the anogenital mucous membrane. While this observation suggests that either the primary infection induces an inadequate immune response or that the virus has developed the ability to avoid immune surveillance, other observations suggest that the immune system is active during primary manifestation as well as during malignant progression of papilloma virus infections [Altmann et al. in VIRUSES AND CANCER, Minson et al., (eds.) Cambridge University Press, (1994) pp. 71-80].
For example, the clinical manifestation of primary infection by rabbit and bovine papilloma virus can be prevented by vaccination with wart extracts or viral structural proteins [Altmann, et al., supra; Campo, Curr. Top. In Microbiol and Immunol. 186:255-266 (1994); Yindle and Frazer, Curr. Top. In Microbiol. and Immunol. 186;217-253 (1994)]. Rodents previously vaccinated with vaccinia recombinants encoding HPV 16 early proteins E6 or E7, or with synthetic E6 or B7 peptides, are similarly protected from tumor formation after inoculation of HPV 16 transformed autologous cells [Altman, et al., supra; Campo, et al., supra; Yindle and Frazer, et al. supra]. Regression of warts can be induced by the transfer of lymphocytes from regressor animals following infection by animal papilloma viruses. Finally, in immunosuppressed patients, such as, for example, recipients of organ transplants or individuals infected with HIV, the incidence of genital warts. CIN, and anogenital cancer is elevated.
To date, no HPV vaccinations have been described which comprise human papilloma virus late L1 protein in the form of capsomeres which are suitable both for prophylactic and therapeutic purposes. Since the L1 protein is not present in malignant genital lesions, vaccination with L1 protein does not have any therapeutic potential for these patients. Construction of chimeric proteins, comprising amino acid residues from L1 protein and, for example E6 or E7 protein, which give rise to chimeric capsomeres, combines prophylactic and therapeutic functions of a vaccine. A method for high level production of chimeric capsomeres would therefore be particularly desirable, in view of the possible advantages offered by such a vaccine for prophylactic and therapeutic intervention.
Thus there exists a need in the art to provide vaccine formulations which can prevent or treat HPV infection. Methods to produce vaccine formulations which overcome problems known in the art to be associated with recombinant HPV protein expression and purification would manifestly be useful to treat the population of individuals already infected with HPV as well as useful to immunize the population of individuals susceptible to HPV infection.
The present invention provides therapeutic and prophylactic vaccine formulations comprising chimeric human papilloma capsomeres. The invention also provides therapeutic methods for treating patients infected with an HPV as well as prophylactic methods for preventing HPV infection in a susceptible individual. Methods for production and purification of capsomeres and proteins of the invention are also contemplated.
In one aspect of the invention, prophylactic vaccinations for prevention of HPV infection are considered which incorporate the structural proteins L1 and L2 of the papilloma virus. Development of a vaccine of this type faces significant obstacles because papilloma viruses cannot be propagated to adequate titers in cell cultures or other experimental systems to provide the viral proteins in sufficient quantity for economical vaccine production. Moreover, recombinant methodologies to express the proteins are not always straightforward and often results in low protein yield. Recently, virus-like particles (VLPs), similar in make up to viral capsid structures, have been described which are formed in Sf-9 insect cells upon expression of the viral proteins L1 and L2 (or L1 on its own) using recombinant vaccinia or baculovirus. Purification of the VLPs can be achieved very simply by means of centrifugation in CsCl or sucrose gradients [Kimbauer, et al., Proc. Natl. Acad. Sci. (USA), 99:12180-12814 (1992): Kirnbaurer, et al., J. Virol. 67:6929-6936 (1994); Proso, et al., J. Virol. 6714:1936-1944 (1992): Sasagawa, et al., Virology 2016:126-195 (1995): Volpers, et al., J. Virol. 69:3258-3264 (1995); Zhou, et al., J. Gen. Virol. 74:762-769 (1993): Zhou, et al., Virology 185:251-257 (1991)]. WO 93/02184 describes a method in which papilloma virus-like particles (VLPs) are used for diagnostic applications or as a vaccine against infections caused by the papilloma virus. WO 94/00152 describes recombinant production of L1 protein which mimics the conformational neutralizing epitope on human and animal papilloma virions.
In another aspect of the invention, therapeutic vaccinations are provided to relieve complications of, for example, cervical carcinoma or precursor lesions resulting from papilloma virus infection, and thus represent an alternative to prophylactic intervention. Vaccinations of this type may comprise early papilloma virus proteins, principally E6 or E7, which are expressed in the persistently infected cells. It is assumed that, following administration of a vaccination of this type, cytotoxic T-cells might be activated against persistently infected cells in genital lesions. The target population for therapeutic intervention is patients with HPV-associated pre-malignant or malignant genital lesions. PCT patent application WO 93/20844 discloses that the early protein E7 and antigenic fragments thereof of the papilloma virus from HPV or BPV is therapeutically effective in the regression, but not in the prevention, of papilloma virus tumors in mammals. While early HPV proteins have been produced by recombinant expression in E. coli or suitable eukaryotic cell types, purification of the recombinant proteins has proven difficult due to inherent low solubility and complex purification procedures which generally require a combination of steps, including ion exchange chromatography, gel filtration and affinity chromatography.
According to the present invention, vaccine formulations comprising papilloma virus capsomeres are provided which comprise either: (i) a first protein that is an intact viral protein expressed as a fusion protein comprised in part of amino acid residues from a second protein; (ii) a truncated viral protein: (iii) a truncated viral protein expressed as a fusion protein comprised in part of amino acid residues from a second protein, or (iv) some combination of the three types of proteins. According to the invention, vaccine formulations are provided comprising capsomeres of bovine papilloma virus (BPV) and human papilloma virus. Preferred bovine virus capsomeres comprise protein from bovine papilloma virus type I. Preferred human virus capsomeres comprise proteins from any one of human papilloma virus strains HPV6, HPV11, HPV16, HPV18, HPV33, HPV35, and HPV45. The most preferred vaccine formulations comprise capsomeres comprising proteins from HPV16.
In one aspect, capsomere vaccine formulations of the invention comprise a first intact viral protein expressed as a fusion protein with additional amino acid residues from a second protein. Preferred intact viral proteins are the structural papilloma vial proteins L1 and L2. Capsomeres comprised of intact viral protein fusions may be produced using the L1 and L2 proteins together or the L1 protein alone. Preferred capsomeres are made up entirely of L1 fusion proteins, the amino acid sequence of which is set out in SEQ ID NO: 2 and encoded by the polynucleotide sequence of SEQ ID NO: 1. Amino acids of the second protein can be derived from numerous sources (including amino acid residues from the first protein) as long as the addition of the second protein amino acid residues to the first protein permits formation of capsomeres. Preferably, addition of the second protein amino acid residues inhibits the ability of the intact viral protein to form virus-like particle structures; most preferably, the second protein amino acid residues promote capsomere formation. In one embodiment of the invention, the second protein may be any human tumor antigen, viral antigen, or bacterial antigen which is important in stimulating an immune response in neoplastic or infectious disease states. In a preferred embodiment, the second protein is also a papilloma virus protein. It also preferred that the second protein be the expression product of papilloma virus early gene. It is also preferred, however, that the second protein be selected from group of E1, E2, E3, E4, E5, E6, and E7xe2x80x94early gene products encoded in the genome of papilloma virus strains HVP6, HPV11, HPV18, HPV33, HPV35, or HPV 45. It is most preferred that the second protein be encoded by the HPV16 E7 gene, the open reading frame of which is set out in SEQ ED NO: 3. Capsomeres assembled from fusion protein subunits are referred to herein as chimeric capsomeres. In one embodiment, the vaccine formulation of the invention is comprised of chimeric capsomeres wherein L1 protein amino acid residues make up approximately 50 to 99% of the total fusion protein amino acid residues. In another embodiment, L1 amino acid residues make up approximately 60 to 90% of the total fusion protein amino acid residues; in a particularly preferred embodiment, L1 amino acids comprise approximately 80% of the fusion protein amino acid residues.
In another aspect of the invention, capsomere vaccine formulations are provided that are comprised of truncated viral proteins having a deletion of one or more amino acid residues necessary for formation of a virus-like particle. It is preferred that the amino acid deletion not inhibit formation of capsomeres by the truncated protein, and it is most preferred that the deletion favor capsomere formation. Preferred vaccine formulations of this type include capsomeres comprised of truncated L1 with or without L2 viral proteins. Particularly preferred capsomeres are comprised of truncated L1 proteins. Truncated proteins contemplated by the invention include those having one or more amino acid residues deleted from the carboxy terminus of the protein, or one or more amino acid residues deleted from the amino terminus of the protein, or one or more amino acid residues deleted from an internal region (i.e., not from either terminus) of the protein. Preferred capsomere vaccine formulations are comprised of proteins truncated at the carboxy terminus. In formulations including L1 protein derived from HPV16, it is preferred that from 1 to 34 carboxy terminal amino acid residues are deleted. Relatively shorter deletions are also contemplated which offer the advantage of minor modification of the antigenic properties of the L1 proteins and the capsomeres formed thereof. It is most preferred, however, that 34 amino acid residues be deleted from the L1 sequence, corresponding to amino acids 472 to 505 in HPV16 set out in SEQ ID NO: 2, and encoded by the polynucleotide sequence corresponding to nucleotides 1414 to 1516 in the human HPV16 L1 coding sequence set out in SEQ ID NO: 1.
When a capsomere vaccine formulation is made up of proteins bearing an internal deletion, it is preferred that the deleted amino acid sequence comprise the nuclear localization region of the protein. In the L1 protein of HPV 16, the nuclear localization signal is found from about amino acid residue 499 to about amino acid residue 505. Following expression of L1 proteins wherein the NLS has been deleted, assembly of capsomere structures occurs in the cytoplasm of the host cell. Consequently, purification of the capsomeres is possible from the cytoplasm instead of from the nucleus where intact L1 proteins assemble into capsomeres. Capsomeres which result from assembly of truncated proteins wherein additional amino acid sequences do not replace the deleted protein sequences are necessarily not chimeric in nature.
In still another aspect of the invention, capsomere vaccine formulations are provided comprising truncated viral protein expressed as a fusion protein adjacent amino acid residues from a second protein. Preferred truncated viral proteins of the invention are the structural papilloma viral proteins L1 and L2. Capsomeres comprised of truncated viral protein fusions may he produced using L1 and L2 protein components together or L1 protein alone. Preferred capsomeres are those comprised of L1 protein amino acid residues. Truncated viral protein components of the fusion proteins include those having one or more amino acid residues deleted from the carboxy terminus of the protein, or one or more amino acid residues deleted from the amino terminus of the protein, or one or more amino acid residues deleted from an internal region (i.e., not from either terminus) of the protein. Preferred capsomere vaccine formulations are comprised of proteins truncated at the carboxy terminus. In those formulations including L1 protein derived from HPV16, it is preferred that from 1 to 34 carboxy terminal amino acid residues are deleted. Relatively shorter deletions are also contemplated that offer the advantage of minor modification of the antigenic properties of the L1 protein component of the fusion protein and the capsomeres formed thereof. It is most preferred, however, that 34 amino acid residues be deleted from the L1 sequence, corresponding to amino acids 472 to 505 in HPV16 set out in SEQ ID NO: 2, and encoded by the polynucleotide sequence corresponding to nucleotides 1414 to 1516 in the human HPV16 L1 coding sequence set out in SEQ ID NO: 1. When the vaccine formulation is comprised of capsomeres made up of proteins bearing an internal deletion, it is preferred that the deleted amino acid sequence comprise the nuclear localization region, or sequence, of the protein.
Amino acids of the second protein can be derived from numerous sources as long as the addition of the second protein amino acid residues to the first protein permits formation of capsomeres. Preferably, addition of the second protein amino acid residues promotes or favors capsomere formation. Amino acid residues of the second protein can be derived from numerous sources, including amino acid residues from the first protein. In a preferred embodiment, the second protein is also a papilloma virus protein. It also preferred that the second protein be the expression product of papilloma virus early gene. It is most preferred, however, that the second protein be selected from group of early gene products encoding by papilloma virus E1, E2, B, E4, E5, E6, and E7 genes. In one embodiment, the vaccine formulation of the invention is comprised of chimeric capsomeres wherein L1 protein amino acid residues make up approximately 50 to 99% of the total fusion protein amino acid residues. In another embodiment, L1 amino acid residues make up approximately 60 to 90% of the total fusion protein amino acid residues; in a particularly preferred embodiment, L1 amino acids comprise approximately 80% of the fission protein amino acid residues.
In a preferred embodiment of the invention, proteins of the vaccine formulations are produced by recombinant methodologies, but in formulations comprising intact viral protein, the proteins may be isolated from natural sources. Intact proteins isolated from natural sources may be modified in vitro to include additional amino acid residues to provide a fusion protein of the invention using covalent modification techniques well known and routinely practiced in the art. Similarly, in formulations comprising truncated viral proteins the proteins may be isolated from natural sources as intact proteins and hydrolyzed in vitro using chemical hydrolysis or enzymatic digestion with any of a number of site-specific or general proteases, the truncated protein subsequently modified to include additional amino acid resides as described above to provide a truncated fusion protein of the invention.
In producing capsomeres, recombinant molecular biology techniques can be utilized to produce DNA encoding either the desired intact protein, the truncated protein, or the truncated fusion protein. Recombinant methodologies required to produce a DNA encoding a desired protein are well known and routinely practiced in the art. Laboratory manuals, for example Sambrook, et al., (eds.), MOLECULAR CLONING: A LABORATORY MANUAL. Cold Spring Harbor Press: Cold Spring Harbor, N.Y. (1989) and Ausebel et al., (eds.). PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley and Sons. Inc. (1994-1997), describe in detail techniques necessary to carry out the required DNA manipulations. For large-scale production of chimeric capsomeres, protein expression can be carried out using either viral or eukaryotic vectors. Preferable vectors include any of the well known prokaryotic expression vectors, recombinant baculoviruses, COS cell specific vectors, vaccinia recombinants, or yeast-specific expression constructs. When recombinant proteins are used to provide capsomeres of the invention, the proteins may first be isolated from the host cell of its expression and thereafter incubated under conditions which permit self-assembly to provide capsomeres. Alternatively, the proteins may be expressed under conditions wherein capsomeres are formed in the host cell.
The invention also contemplates processes for producing capsomeres of the vaccine formulations. In one method, L1 proteins are expressed from DNA encoding six additional histidines at the carboxy terminus of the L1 protein coding sequence L1 proteins expressed with additional histidines (His L1 proteins) are most preferably expressed in E. coli and the His L1 proteins can be purified using nickel affinity chromatography. His L1 proteins in cell lysate are suspended in a denaturation buffer, for example, 6 M guanidine hydrochloride or a buffer of equivalent denaturing capacity, and then subjected to nickel chromatography. Protein eluted from the nickel chromatography step is renatured, for example in 150 mM NaCl, 1 mM CaCl2, 0.01% Triton-X 100, 10 mM HEPES (N-2-hydroxymethyl piperazine-Nxe2x80x2-2 ethane sulfonic acid), pH 7.4. According to a preferred method of the invention, assembly of capsomeres takes place after dialysis of the purified proteins, preferably after dialysis against 150 mM NaCl, 25 mM Ca2+, 10% DMSO (dimethyl sulfoxide). 0.1% Triton-X 100. 10 mM Tris [tris-(hydroxymethyl) amino-methane] acetic acid with a pH value of 5.0.
Formation of capsomeres can be monitored by electron microscopy, and, in instances wherein capsomeres are comprised of fusion proteins, the presence of various protein components in the assembled capsomere can be confirmed by Western blot analysis using specific antisera.
According to the present invention, methods are provided for therapeutic treatment of individuals infected with HPV comprising the step of administering to a patient in need thereof an amount of a vaccine formulation of the invention effective to reduce the level of HPV infection. The invention also provide methods for prophylactic treatment of individuals susceptible to HPV infection comprising the step of administering to an individual susceptible to HPV infection an amount of a vaccine formulation of the invention effective to prevent HPV infection. While infected individuals can be easily identified using standard diagnostic techniques, susceptible individuals may be identified, for example, as those engaged in sexual relations with an infected individual. However, due to the high frequency of HPV infection, all sexually active persons are susceptible to papilloma virus infection.
Administration of a vaccine formulation can include one or more additional components such as pharmaceutically acceptable carriers, diluents, adjuvants, and/or buffers. Vaccines may be administered at a single time or at multiple times. Vaccine formulation of the invention may be delivered by various routes including, for example, oral, intravenous, intramuscular, nasal, rectal, transdermal, vaginal, subcutaneous, and intraperitoneal administration.
Vaccine formulations of the invention offer numerous advantages when compared to conventional vaccine preparations. As part of a therapeutic vaccination, capsomeres can promote elimination of persistently infected cells in, for example, patients with CIN or cervical carcinoma. Additionally, therapeutic vaccinations of this type can also serve a prophylactic purpose in protecting patients with CIN lesions from re-infection. As an additional advantage, capsomeres can escape neutralization by pre-existing anticapsid antibodies and thereby posses longer circulating half-life as compared to chimeric virus-like particles.
Vaccine formulations comprising chimeric capsomeres can provide the additional advantage of increased antigenicity of both protein components of the fusion protein from which the capsomere is formed. For example, in a VLP, protein components of the underlying capsomere may be buried in the overall structure as a result of internalized positioning within the VLP itself. Similarly, epitopes of the protein components may be sterically obstructed as, a result of capsomere-to-capsomere contact, and therefore unaccessible for eliciting an immune response. Preliminary results using L1/E7 fusion proteins to produce VLPs support this position in that no antibody response was detected against the E7 component. This observation is consistent with previous results which indicate that the carboxy terminal region of L1 forms inter-pentameric arm structures that allow assembly of capsomeres into capsids [Garcia, et al., J. Virol. 71: 2988-2995 (1997)]. Presumably in a chimeric capsomere structure, both protein components of the fusion protein substructure are accessible to evoke an immune response. Capsomere vaccines would therefore offer the additional advantage of increased antigenicity against any protein component, including, for example, neutralizing epitopes from other virus proteins, expressed as a fusion with L1 amino acid sequences.
The present invention is illustrated by the following examples. Example 1 describes construction of expression vectors to produce fusion, or chimeric, viral proteins. Example 2 relates to generation of recombinant baculoviruses for expression of viral proteins. Example 3 addresses purification of capsomeres. Example 4 describes an immunization protocol for production of antisera and monoclonal antibodies. Example 5 provides a peptide ELISA to quantitate capsomere formation. Example 6 describes an antigen capture ELISA to quantitate capsomere formation. Example 7 provides a hemagglutinin assay to assay for the induction of neutralizing antibodies.